Black Blood Vial

Description:

This viscous, tar-black liquid is stored in a jagged glass vial sealed with bone and wax. The potion smells of iron, rot, and burnt herbs, and it trembles with a pulse of latent necromantic energy. Said to be created using forbidden rites and cursed vitae, drinking the vial tricks the body into rapid, unnatural regeneration — but the cost is etched deep into the flesh and soul.

Effect:

Upon consumption, the drinker instantly gains the equivalent benefits of a Long Rest, including restored HP, expended spell slots, and abilities — as if they'd completed a full night’s rest.
Downside: After 1 hour, the user must make a DC 16 Constitution saving throw or become Cursed for 24 hours. While cursed, they:
regain 1/2 hp from all sources rounded down.
Have disadvantage on saving throws against necrotic damage and exhaustion
Are considered vulnerable to critical hits (your opponent crits you on 1 dice roll higher

Crafting Recipe

Crafting Check: DC 15 Intelligence (Alchemist’s Supplies) or Wisdom (Herbalism Kit)

Required Components:

Vial of Cursed Blood from a creature that died under a potent curse (undead or cursed humanoid)
Darkroot Sap, harvested only during the new moon
Powdered Obsidian Spike, ground fine to stabilize the brew

Component Search DCs:

Vial of Cursed Blood: DC 14 Arcana or Medicine (requires appropriate corpse or enemy defeat)
Darkroot Sap: DC 15 Nature or Survival (must be harvested during a specific phase, usually a downtime activity)
Obsidian Spike (powdered): DC 10 to craft from an Obsidian Spike item